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Edited by Michael E. Fisher, University of Maryland, College Park, MD, and approved March 12, 2010 (received for review October 13, 2009)
Abstract
The actomyosin molecular motor, the motor composed of myosin II and actin filament, is responsible for muscle contraction, converting chemical energy into mechanical work. Although recent single molecule and structural studies have shed new light on the energy-converting mechanism, the physical basis of the molecular-level mechanism remains unclear because of the experimental limitations. To provide a clue to resolve the controversy between the lever-arm mechanism and the Brownian ratchet-like mechanism, we here report an in silico single molecule experiment of an actomyosin motor. When we placed myosin on an actin filament and allowed myosin to move along the filament, we found that myosin exhibits a unidirectional Brownian motion along the filament. This unidirectionality was found to arise from the combination of a nonequilibrium condition realized by coupling to the ATP hydrolysis and a ratchet-like energy landscape inherent in the actin-myosin interaction along the filament, indicating that a Brownian ratchet-like mechanism contributes substantially to the energy conversion of this molecular motor.
- molecular machines
- molecular motors
- mechano-chemical coupling
- molecular dynamics simulation
- functional funnel
Footnotes
- 1To whom correspondence should be addressed. E-mail: mtkn{at}waseda.jp.
Author contributions: M.T., T.P.T., and M.S. designed research; M.T. performed research; M.T. and T.P.T. contributed new reagents/analytic tools; M.T. analyzed data; and M.T., T.P.T., and M.S. wrote the paper.
The authors declare no conflict of interest.
This article is a PNAS Direct Submission.
This article contains supporting information online at www.pnas.org/cgi/content/full/0911830107/DCSupplemental.
Unidirectional Brownian motion observed in an in silico single molecule experiment of an actomyosin motor
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